The good news is, as they fight more, they also become exponentially more affectionate. I have proof:
When we walk down the sidewalk, anytime Jubee gets within 10 feet of the corner, Sammy runs in front of her and bodily blocks the path so she can't walk in the street. That's good-brotherness.
Sometimes, they are playing different games at the park and realize they are far away from each other. One will yell to the other, and they both take off running. Embrace. And scene.
In my head, it's in slow motion, with that bit from Tchaikovsky's "Romeo and Juliet" playing in the background. In reality, Sammy knocks her over 50% of the time and she cries.
And sometimes I can even get in on this action. Nice.